Some embodiments described herein relate generally to methods and apparatus for determining a birefringence axis of a polarization-maintaining optical fiber.
Some known techniques for determining a birefringence axis in a polarization-maintaining optical fiber can be classified into one of two types of techniques: a side viewing technique and an end viewing technique. A side viewing technique can include, for example, illuminating and imaging through the side of the fiber and/or analyzing an output image to infer internal fiber structure. In general, this type of technique can have limited accuracy in determining the birefringence axis and the core position of the fiber because this type of technique does not directly measure the fiber's internal structure. End viewing techniques can also have a number of drawbacks. For example, an end view technique can be sensitive to end face artifacts, can be difficult to find features in the end face due to poor contrast and lack of dynamic range in the imaging sensor, and/or can often involve user input regarding position and/or size of birefringence axis defining features. In some cases, a user may not know these parameters or may input erroneous parameters, compromising system performance. Thus, a need exists for improved devices and methods for determining a birefringence axis of a polarization-maintaining optical fiber.